分类： 生物学 >> 生物物理学 >> 神经科学 提交时间： 2016-05-12
摘要： The brain constantly creates perceptual predictions about forthcoming stimuli to guide perception efficiently. Abundant studies have demonstrated that perceptual predictions modulate sensory activities depending on whether the actual inputs are consistent with one particular prediction. In real-life contexts, however, multiple and even conflicting predictions might concurrently exist to be tested, requiring a multiprediction coordination process. It remains largely unknown how multiple hypotheses are conveyed and harmonized to guide moment-by-moment perception. Based on recent findings revealing that multiple locations are sampled alternatively in various phase of attentional rhythms, we hypothesize that this oscillation-based temporal organization mechanism may also underlie the multiprediction coordination process. To address the issue, we used well established priming paradigms in combination with a time-resolved behavioral approach to investigate the fine temporal dynamics of the multiprediction harmonization course in human subjects. We first replicate classical priming effects in slowly developing trends of priming time courses. Second, after removing the typical priming patterns, we reveal a new theta-band (similar to 4 Hz) oscillatory component in the priming behavioral data regardless of whether the prime was masked. Third, we show that these theta-band priming oscillations triggered by congruent and incongruent primes are in an out-of-phase relationship. These findings suggest that perceptual predictions return to low-sensory areas not continuously but recurrently in a theta-band rhythm (every 200-300 ms) and that multiple predictions are dynamically coordinated in time by being conveyed in different phases of the theta-band oscillations to achieve dissociated but temporally organized neural representations.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2018-04-24 合作期刊: 《干旱区科学》
摘要： Grazing exclusion is one of the most efficient approaches to restore degraded grassland but may negatively affects the recovery of species diversity. Changes in plant species diversity should be a consequence of the ecological assembly process. Local community assembly is influenced by environmental filtering, biotic interactions, and dispersal. However, how these factors potentially contribute to changes to species diversity is poorly understood, especially in harsh environments. In this study, two management sites within a Stipa breviflora desert steppe community (typical natural steppe) were selected in northern China. In one of the two management sites, grazing has been excluded since 2010 and in the other with open grazing by sheep. In August 2016, three plots were established and 100 sampling units were created within each plot in a 5 m×5 m area at the two management sites. To assess the effects of grazing exclusion on S. breviflora steppe, we analyzed the vegetation biomass, species diversity, soil organic carbon, and soil particle size distribution using paired T-tests. In addition, variation partitioning was applied to determine the relative importance of environmental filtering and dispersal limitation. Null mode analysis was used to quantify the influence of biotic interactions in conjunction with EcoSim niche overlap and co-occurrence values. Our results demonstrated that (1) species diversity significantly decreased and the main improvements in soil quality occurred in the topsoil 0–10 cm after the grazing exclusion; (2) environmental filtering was important for community assembly between grazed and fenced grassland and this appears particularly true for soil particle size distribution, which may be well correlated with soil hydrological processes; and (3) however, competitive exclusion may play a significant role within the exclusion. The multiple pathways of assembly may collectively determine negative effects on the restoration of species diversity. Therefore, designers should be aware of the risk of reducing grazing exclusion-induced species diversity and account for manipulating processes. This in turn will reduce dominant species and promote environmental heterogeneity to maximize species diversity in semi-arid regions.
分类： 生物学 >> 生物物理学 提交时间： 2016-05-12
摘要： What is a number? The number sense hypothesis suggests that numerosity is "a primary visual property" like color, contrast, or orientation. However, exactly what attribute of a stimulus is the primary visual property and determines numbers in the number sense? To verify the invariant nature of numerosity perception, we manipulated the numbers of items connected/enclosed in arbitrary and irregular forms while controlling for low-level features (e.g., orientation, color, and size). Subjects performed discrimination, estimation, and equality judgment tasks in a wide range of presentation durations and across small and large numbers. Results consistently show that connecting/enclosing items led to robust numerosity underestimation, with the extent of underestimation increasing monotonically with the number of connected/enclosed items. In contrast, grouping based on color similarity had no effect on numerosity judgment. We propose that numbers or the primitive units counted in numerosity perception are influenced by topological invariants, such as connectivity and the inside/outside relationship. Beyond the behavioral measures, neural tuning curves to numerosity in the intraparietal sulcus were obtained using functional MRI adaptation, and the tuning curves showed that numbers represented in the intraparietal sulcus were strongly influenced by topology.
分类： 生物学 >> 生态学 提交时间： 2023-10-17 合作期刊: 《干旱区科学》
摘要： Changes in precipitation and nitrogen (N) addition may significantly affect the processes of soil carbon (C) cycle in terrestrial ecosystems, such as soil respiration. However, relatively few studies have investigated the effects of changes in precipitation and N addition on soil respiration in the upper soil layer in desert steppes. In this study, we conducted a control experiment that involved a field simulation from July 2020 to December 2021 in a desert steppe in Yanchi County, China. Specifically, we measured soil parameters including soil temperature, soil moisture, total nitrogen (TN), soil organic carbon (SOC), soil microbial biomass carbon (SMBC), soil microbial biomass nitrogen (SMBN), and contents of soil microorganisms including bacteria, fungi, actinomyces, and protozoa, and determined the components of soil respiration including soil respiration with litter (RS+L), soil respiration without litter (RS), and litter respiration (RL) under short-term changes in precipitation (control, increased precipitation by 30%, and decreased precipitation by 30%) and N addition (0.0 and 10.0 g/(m2a)) treatments. Our results indicated that short-term changes in precipitation and N addition had substantial positive effects on the contents of TN, SOC, and SMBC, as well as the contents of soil actinomyces and protozoa. In addition, N addition significantly enhanced the rates of RS+L and RS by 4.8% and 8.0% (P0.05). The mean RL/RS+L value observed under all treatments was 27.63%, which suggested that RL is an important component of soil respiration in the desert steppe ecosystems. The results also showed that short-term changes in precipitation and N addition had significant interactive effects on the rates of RS+L, RS, and RL (P
分类： 医学、药学 >> 基础医学 提交时间： 2023-09-28
Chang, Zhengyao
Li, Jiyang
Zhang, Chao
Gao, Yunhe
Liang, Wenquan
Pan, Heng
Zhang, Kecheng
Cui, Jianxin
Wei, Bo
Chen,Lin
Xi,Hongqing
摘要： Objective: Liver metastasis is one of the major causes of cancer-related death in gastric cancer (GC) patients. This study was to investigate the roles of THBS2 in the tumorigenesis and liver metastasis of GC and the sensitivity of GC to trastuzumab.Methods: Sequencing was employed to identify the differentially expressed genes in the GC. The THBS2 expression was detected in GC tissues and GC cell lines, its relationships with clinicopathological characteristics were further assessed, and its roles in the malignant behaviors of GC were further investigated in vitro and in vivo, by up-regulating or down-regulating THBS2 expression. The PTEN and its downstream AKT and FAK signaling pathways were investigated in the GC aiming to explore the potential mechanism underlying the regulatory effects of THBS2.Results: THBS2 expression increased significantly in the GC as compared to the normal gastric tissues, which was related to the distal metastasis and poor prognosis of GC patients. THBS2 expression also increased in the primary GC cells and human gastric cell line NCI-N87. THBS2 downregulation induced mesenchymal-epithelial transition (MET) and PTEN nuclear translocation, which inhibited the metastasis of GC cells. Carmofur promoted PTEN nuclear translocation, inhibiting the metastases and THBS2 downregulation together with carmofur improved the sensitivity of GC to trastuzumab.Conclusions: THBS2 is overexpressed in GC tissues of patients with synchronous liver metastases and its overexpression is associated with poor prognosis. THBS2 downregulation inhibits the metastases of GC. THBS2 down-regulation and carmofur can be used as a new treatment for the advanced GC with metastases.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Jieyuan Cui
Yang Liu
Yunzhou Deng
Chen Lin
Zhishan Fang
Chensheng Xiang
Peng Bai
Kai Du
Xiaobing Zuo
Kaichuan Wen
Shaolong Gong
Haiping He
Zhizhen Ye
Yunan Gao
He Tian
Baodan Zhao
Jianpu Wang
Yizheng Jin
摘要： Solution-processed planar perovskite light-emitting diodes (LEDs) promise high-performance and cost-effective electroluminescent (EL) devices ideal for large-area display and lighting applications. Exploiting emission layers with high ratios of horizontal transition dipole moments (TDMs) is expected to boost photon outcoupling of planar LEDs. However, LEDs based on anisotropic perovskite nanoemitters remains to be inefficient (external quantum efficiency, EQE <5%), due to the difficulties of simultaneously controlling the orientations of TDMs, achieving high photoluminescence quantum yields (PLQYs) and realizing charge balance in the films of the assembled nanostructures. Here we demonstrate efficient EL from an in-situ grown continuous perovskite film comprising of a monolayer of face-on oriented nanoplatelets. The ratio of horizontal TDMs of the perovskite nanoplatelet films is ~84%, substantially higher than that of isotropic emitters (67%). The nanoplatelet film shows a high PLQY of ~75%. These merits enable LEDs with a peak EQE of 23.6%, representing the most efficient perovskite LEDs.
分类： 生物学 >> 生物物理学 提交时间： 2016-05-12
Qin, Dongdong
Rizak, Joshua
Chu, Xunxun
Li, Zhifei
Yang, Shangchuan
Feng, Xiaoli
Hu, Xintian
Qin, Dongdong
Rizak, Joshua
Chu, Xunxun
Li, Zhifei
Yang, Shangchuan
Feng, Xiaoli
Hu, Xintian
Qin, Dongdong
Chen, Lin
Lu, Longbao
Hu, Xintian
Yang, Lichuan
Yang, Lichuan
摘要： Non-human primates offer unique opportunities to study the development of depression rooted in behavioral and physiological abnormalities. This study observed adult female rhesus macaques within social hierarchies and aimed to characterize the physiological and brain abnormalities accompanying depressive-like behavior. The behaviors of 31 female rhesus macaques from 14 different breeding groups were video recorded, and the footage was analyzed using the focal animal technique. There were 13 monkeys who never displayed huddling behavior (non-huddlers). The remaining 18 monkeys were divided into two groups according the mean time spent in the huddle posture. Four monkeys were designated as high huddlers, whereas the other 14 monkeys were low huddlers. An inverse relationship was discovered between social rank and depression. High huddlers spent more time engaging in physical contact and in close proximity to other monkeys, as well as less time spontaneously and reactively locomoting, than low huddlers and/or non-huddlers. Cortisol levels measured from the hair were elevated significantly in high huddlers compared with low huddlers and non-huddlers, and the measured cortisol levels were specifically higher in high huddlers than subordinate or dominant control monkeys. Regional cerebral blood flow data revealed significant and widespread decreases in high huddlers compared with non-huddlers.
分类： 生物学 >> 生物物理学 提交时间： 2016-05-12
Wei, Pengfei
Liu, Nan
Liu, Xuemei
Tang, Yongqiang
Wu, Bifeng
Zhou, Zheng
Liu, Yaohan
Li, Juan
Zhang, Yi
Wang, Liping
Wei, Pengfei
Liu, Nan
Liu, Xuemei
Tang, Yongqiang
Wu, Bifeng
Zhou, Zheng
Liu, Yaohan
Li, Juan
Zhang, Yi
Wang, Liping
摘要： The ability of animals to respond to life-threatening stimuli is essential for survival. Although vision provides one of the major sensory inputs for detecting threats across animal species, the circuitry underlying defensive responses to visual stimuli remains poorly defined. Here, we investigate the circuitry underlying innate defensive behaviours elicited by predator-like visual stimuli in mice. Our results demonstrate that neurons in the superior colliculus (SC) are essential for a variety of acute and persistent defensive responses to overhead looming stimuli. Optogenetic mapping revealed that SC projections to the lateral posterior nucleus (LP) of the thalamus, a non-canonical polymodal sensory relay, are sufficient to mimic visually evoked fear responses. In vivo electrophysiology experiments identified a di-synaptic circuit from SC through LP to the lateral amygdale (Amg), and lesions of the Amg blocked the full range of visually evoked defensive responses. Our results reveal a novel collicular-thalamic-Amg circuit important for innate defensive responses to visual threats.
点击量
待评议
点击量
下载量
评论
